Blowing fuses

[Jayboundless]

Hi all, Let me first start off by saying that electrics make my brain hurt. Here's my question. I have a 1969 911 T and the third fuse from the top which is labeled cigarette lighter, clock, glove compartment light, interior lamps. This fuse keeps blowing and gave me a bit of a shockwhen reinstalling a new fuse. Does this mean that I have a bad ground or some wiring problem at specifically one of those items? Where do I start in testing the circuit?

Thanks in advance!


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[timmy2]

Do you have an ohmmeter?
Leave the fuse out and check the load side (wire to devices listed) to ground and see if there is a short to ground.
If yes, start at the hood lamps and see if the black power supply wiring to them is chaffed, melted or otherwise looks ok, disconnect them and see if the ground goes away. Then move to all the other devices on the list and do the same. The glove box lamp is notorious for falling out and shorting to the dash metal causing all sorts of mayhem in the wiring for the circuits attached to it... Melted wires to multiple circuits all over....

[911pcars]

Originally Posted by Jayboundless

Hi all, Let me first start off by saying that electrics make my brain hurt. Here's my question. I have a 1969 911 T and the third fuse from the top which is labeled cigarette lighter, clock, glove compartment light, interior lamps. This fuse keeps blowing and gave me a bit of a shockwhen reinstalling a new fuse. Does this mean that I have a bad ground or some wiring problem at specifically one of those items? Where do I start in testing the circuit?

Thanks in advance!

Since you already isolated the offending circuit:
"third fuse from the top which is labeled cigarette lighter, clock, glove compartment light, interior lamps "

As Jayboundless suggests, you can use a continuity tester (ohmmeter) on the load side of the fuse (better disconnect battery first). Load = electrical accessory (bulb, clock, radio, motor, etc.).

While observing the resistance display, remove the elec. connector from each branch circuit load in turn and see if any of those devices is the source of the short circuit (bypassing the load). Could also be a bare wire in any of the circuit wires leading to those loads. Try wiggling the circuit wire and see if it makes any difference in the resistance (continuity) display.

With the suspected load disconnected, you should be able to install a good fuse and restore operation to the remaining loads protected by fuse #3. In many cases, the load may have a piggyback connector that leads to the next branch load in fuse circuit #3. Make sure the disconnected connector is insulated from any metal ground.

Once you pinpoint the source of the malfunction, remove and bench test it with the ohmmeter to confirm it is indeed faulty.

Hope this helps,
Sherwood

[wwest]

12 volts isn't enough to shock unless there is an inductive load involved..

[Jayboundless]

Thanks for the direction gents.